p16/INK4a and p15/INK4b gene methylation and absence of p16/INK4a mRNA and protein expression in Burkitt's lymphoma.
The fact that the p16/INK4a and p15/INK4b genes are frequently inactivated in human malignancies and that p16/INK4a null mice spontaneously develop B-cell lymphomas prompted us to examine the status of both genes in Burkitt's Lymphoma (BL). We found a low frequency of p16/INK4a and p15/INK4b deletions and mutations in BL cell lines and biopsies. However, p16/INK4a exon 1 was methylated in 17 out of 19 BL lines (89.5%) and in 8 out of 19 BL biopsies (42%) analyzed. p15/INK4b Exon 1 was also methylated, although at a lower frequency. p16/INK4a mRNA was readily detected in BL lines carrying unmethylated p16/INK4a, but not in those carrying methylated p16/INK4a. No p16/INK4a protein was detected in any of the BL lines and biopsies examined. In contrast, only one out of seven lymphoblastoid cell lines (LCLs) examined was methylated in p16/INK4a exon 1, and three out of the six LCLs with unmethylated p16/INK4a expressed detectable levels of p16/INK4a protein. Thus, the frequent p16/INK4a methylation in BL lines correlates with downregulation of p16/INK4a expression, suggesting that exon 1 methylation is responsible for silencing the p16/INK4a gene in BL.
Klangby
U
U
Microbiology & Tumor Biology Center, Karolinska Institute, Stockholm, Sweden.
Okan
I
I
Magnusson
K P
KP
Wendland
M
M
Lind
P
P
Wiman
K G
KG
D015152:Blotting, Northern; D015139:Blotting, Southern; D002051:Burkitt Lymphoma / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics*; D018797:Cell Cycle Proteins; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics*; D019175:DNA Methylation; D005091:Exons; D017353:Gene Deletion; D015870:Gene Expression; D016158:Genes, p53 / Q000235:genetics; D006801:Humans; D009154:Mutation; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis*; D025521:Tumor Suppressor Proteins
C493966:CDKN2B protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16; D012333:RNA, Messenger; D025521:Tumor Suppressor Proteins